1. Field of The Invention
This invention relates to a recording and reproducing apparatus which has a scrambling function for keeping the contents of a record secret and reproduces the record under restricted reproduction condition.
2. Description of The Related Art
In recent years, there has been achieved notable progress of an apparatus for recording and reproducing a video signal and an audio signal (for example, a video tape recorder). Especially, the development of a recording system from an analogue recording system to a digital recording system has brought an improved high-image-quality and high-sound-quality apparatus into being.
Such an improved apparatus, however, has encountered a problem of protecting the copyrighted contents of a record from illegal copying thereof from media on which the record is recorded.
To resolve such a problem, in the field of digital audio technology, a serial copy management system (SCMS) is introduced for protecting copyrights.
Meanwhile, the improved apparatus has also encountered another problem of keeping the contents of a record secret in case where at the time of recording information (namely, the contents of a record to be recorded), a signal representing the information is scrambled and thereafter, at the time of reproducing the information, a descrambling is performed only when restricted reproduction condition is met.
A conventional recording and reproducing apparatus developed to resolve this problem is disclosed in, for instance, the Japanese Unexamined Patent Publication (Kokai Tokkyo Koho) Official Gazette H4-86177.
Hereinafter, this conventional recording and reproducing apparatus will be outlined.
First, a recording portion of this conventional recording and reproducing apparatus comprises a scrambling circuit for scrambling a video signal and an identification (ID) code generating circuit for generating a proper ID code. Further, a scrambled video signal, as well as an ID code, is sent to a head. Then, the video signal and the ID code are recorded on a recording medium such as magnetic tape. The ID code is recorded in, for example, a vertical-interval time code (VITC) data area.
Moreover, a reproducing portion of this conventional recording and reproducing apparatus comprises a descrambling circuit for descrambling a reproduction video signal and an ID detection circuit for determining whether or not a reproduced ID code matches the proper ID code. Furthermore, only when this ID detection circuit determines that the reproduced ID code matches the proper ID code, the reproducing portion reproduces the video signal by descrambling the reproduction video signal.
Thus, among the conventional apparatuses of a same type, ID codes corresponding to the same information represented by a video signal are made to differ with these apparatuses in case where full compatibility is inconvenient for keeping the information secret. Namely, the compatibility of this conventional apparatus with the conventional apparatus of the same type is limited.
However, in case of this conventional recording and reproducing apparatus, an ID code per se is recorded on the tape (for example, in the VITC data area). Therefore, the ID code can be easily decoded from a reproduction signal. Consequently, this conventional recording and reproducing apparatus has a drawback in that the secrecy of the contents of a record represented by a video signal can be easily violated by specifying an apparatus being capable of reproducing the video signal and by further changing a value set in each apparatus.
Further, this conventional recording and reproducing apparatus has another drawback. Namely, there is no causal relation between the ID code and the scrambling. Thus, if a third person makes his private descrambling apparatus, any video signal recorded by this conventional apparatus can be reproduced by such a descrambling apparatus. Consequently, there is a fear that the scrambling of the video signal may come to mean nothing.
The present invention is accomplished to eliminate the drawbacks of the conventional recording and reproducing apparatus.